The invention concerns a drive device for a moveable furniture part comprising an ejection element, an ejection force storage member (accumulator) and a locking device for the ejection element. The locking device has a locking pin which is acted upon by the ejection force storage member (accumulator) and which is lockable in a locking position in a latching region of a guide path. The guide path has a cardioid-shaped configuration and the cardioid-shaped guide path has a stressing portion in which the locking pin is moveable upon stressing of the ejection force accumulator and a latching engagement movement region of the locking pin before the locking position in the latching region is reached. The invention further concerns an article of furniture comprising a furniture carcass, a furniture part moveable relative to the furniture carcass and such a drive device for the moveable furniture part.
Drive devices for ejecting a moveable furniture part from a closed position into an open position have already been known for many years in the furniture fitting industry. To guarantee that the ejection element or the moveable furniture part is securely held in a closed position, locking devices are provided in that arrangement. When opening of the moveable furniture part is wanted, the locking device can then be unlocked by actuation of a triggering mechanism. Unlocking can be effected for example by pressing against the moveable furniture part to push it into an over-pressing position. Triggering or unlocking is also possible by pulling. After such unlocking an ejection force accumulator can deliver its force and in so doing move the moveable furniture part in the opening direction by way of the ejection element.
After the ejection force accumulator has been relieved of its load upon opening of the moveable furniture part that ejection force must be restored to the ejection force accumulator again by stressing. That is generally effected when closing a moveable furniture part (but it can also be effected upon opening) by an operator who moves the moveable furniture by hand. When therefore a pressing force is applied to the moveable furniture part upon closure thereof, pressure is also applied against the force of the ejection force accumulator. As soon as the ejection force accumulator is fully stressed the locking pin of the locking device passes along the guide path into the latching region, in which case then the hand no longer holds the ejection force accumulator in its stressed position but the locking pin locks or holds the stressed ejection force accumulator in the locking position at the latching region.
A critical region in terms of stressing and locking is the region immediately prior to reaching the locking position in the latching region. More specifically if the latching pin, by virtue of the configuration of the guide path, passes into a region shortly before reaching the latching region, then the ejection force accumulator can act with a relatively high force on that locking pin, in which case that then comes into an abutment condition in the latching region with the production of a relatively large amount of noise and heavy wear.
DE 10 2011 002 212 R1 discloses a spring element which forms a latching recess but which only serves to also permit pulling unlocking.
WO 2007/112463 A2 entails the problem of noise generation, but for that purpose the entire moveable furniture part is braked before the ejection force accumulator is loaded.